Jason Single Groove Cast Iron Pulley AK25-1/2. Outside Diameter 2.5" Bore Size 1/2" 1 Set Screw Included. Designed to fit 3L, 4L and A Belts. Light duty cast iron pulleys are machined from gray cast iron. They are statically balanced, painted and are individually packaged. Available in single and double groove. Bushings are ordered separately.